SQL: how to select a single id (“row”) that meets multiple criteria from a single column

Question

I have a very narrow table: user_id, ancestry.

The user_id column is self explanatory.

The ancestry column contains the country from where the user\'s ancest

Answer 1

Users who have one of the 3 countries

SELECT DISTINCT user_id
FROM table
WHERE ancestry IN('England','France','Germany')

Users who have all 3 countries

SELECT DISTINCT A.userID
FROM table A
   INNER JOIN table B on A.user_id = B.user_id
   INNER JOIN table C on A.user_id = C.user_id
WHERE A.ancestry = 'England'
   AND B.ancestry = 'Germany'
   AND C.ancestry = 'France'